The present invention is generally related to the field of suture anchors. There are many procedures, such as SLAP (Superior Labrum from Anterior to Posterior) and Bankart lesion repairs, or reconstruction of labral tissue to the glenoid rim, in which a surgeon needs to secure tissue in close contact with bone. Often the bone surface is roughened, and when tissue is pulled into intimate contact, the body's healing response will fuse the tissue and bone together.
This procedure is often accomplished by implanting an anchor, pre-loaded with a strand of suture, into a hole drilled in the bone at the desired anchor location. One of the suture ends is then passed through the soft tissue at the desired location, and the suture is secured to the anchor by tying a knot.
There are many suture anchor designs on the market today intended to secure suture, which is passed through soft tissue, to bone. Most of the anchor designs rely on interference between external features on the anchor (barbs, ribs, ridges, etc.) and the hole to provide fixation strength. A high amount of interference results in a large force required to insert the anchor into the bone. These large insertion forces (often imparted by a hammer or mallet) can result in broken anchors, broken insertion tools, or worse, damage to the bone itself. An important step in the procedure is adding tension to the suture to pull the captured tissue into intimate contact with the bone. Many anchors can change the tension in the suture during deployment, which requires the surgeon to estimate how much tension will be added during the final installation step. This can result in under- or over-tensioning of the tissue against the bone. The final step of securing the suture and tissue—tying a knot—has been shown to be a common source of anchor failure. It is also a step that requires a great deal of practice and skill by the surgeon and time during the procedure itself.
Since the knot is often problematic for the reasons stated above, several knotless designs have recently been developed. Some of these are described below:
The Bioknotless™ anchor by DePuy Mitek is a simple anchor which is loaded with a loop of suture secured to the anchor with a knot. The loop is passed through the tissue, then the loop must be hooked in a groove at the tip of the anchor. This step can be tedious and difficult, depending on the angle of approach to the hole. Finally, the anchor is tapped into the hole in the bone. The final tension on the suture loop and attached tissue is controlled by the anchor insertion depth. This requires the surgeon to drill a hole deep enough to achieve sufficient tension. If the bite of tissue through which suture is passed is smaller than expected or achievable, the anchor may reach the bottom of the hole before enough tension is placed on the tissue. This results in the tissue not being pulled firmly against the bone surface and may result in inferior long-term repair strength. Depending on the angle of approach and the location on the bone (such as inferior on the glenoid), it may be impossible to drill a deep enough hole to achieve the desired tension.
Arthrocare has developed the LabraLock P™ anchor. This two-part anchor, made from PEEK (Polyetheretherketone), secures two strands of suture (the strands which form the loop that is passed through the tissue) between the anchor and the bone, and the other two strands (the free ends of suture) between the anchor's inner shaft and the outer, tube portion. The outer tube portion has barbs which secure the anchor in the bone via an interference fit.
The PushLock™ anchor, by Arthrex, is also a two-part anchor. The tip of the anchor has an eyelet through which the suture legs are loaded. This tip is placed at the bottom of a hole drilled into the bone. At this point, the surgeon may adjust the tension on the suture, thereby pulling the tissue closer to the surface of the bone. When the tension is deemed correct, the rear portion of the anchor is driven into the hole. This rear portion is a length of tube which has circumferential barbs on its outer diameter which provide interference to anchor the device in the hole. Since the barbed portion of the anchor is a full cylinder, it can require a great deal of force to insert into a smaller diameter hole, especially in hard bone.
The ConMed Ultrafix Knotless Minimite™ anchor is a knotless anchor made of metal, which many surgeons do not want to deploy within a joint. If the anchor were to pull out of the bone, the metal could cause a great deal of damage rubbing against the articular surfaces—e.g. the humeral head and glenoid.
Smith & Nephew has marketed the KINSA™ suture anchor. It is a knotless design made of PEEK which is tapped into a pre-drilled hole in the bone. The anchor is preloaded with suture tied in a one-way sliding knot within the anchor body, which allows the surgeon to adjust the tension after the anchor has been deployed.